Surveying

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This article is about measuring positions on Earth. For other uses, see Survey.
Center for Operational Oceanographic Products and Services staff member conducts tide station leveling in support of the U.S. Army Corp of Engineers in Richmond, Maine.

Surveying or land surveying is the technique, profession, and science of determining the terrestrial or three-dimensional position of points and the distances and angles between them, practiced by surveyors, and members of various engineering professions. These points are usually on the surface of the Earth, and they are often used to establish land maps and boundaries for ownership, locations like building corners or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.

Surveyors use elements of mathematics (geometry and trigonometry), physics, engineering and the law. Surveying equipment includes total stations, robotic total stations, GPS receivers, prisms, 3D scanners, radios, handheld tablets, digital levels, and surveying software.

Surveying has been an element in the development of the human environment since the beginning of recorded history. It is required in the planning and execution of most forms of construction. Familiar modern uses are in the fields of transport, building and construction, communications, mapping, and the definition of legal boundaries for land ownership.

ACSM definitions[edit]

The American Congress on Surveying and Mapping (ACSM),defines surveying as the science and art of making all essential measurements to determine the relative position of points or physical and cultural details above, on, or beneath the surface of the Earth, and to depict them in a usable form, or to establish the position of points or details.[citation needed]

Also per ACSM, a particular type of surveying known as "land surveying" is the detailed study or inspection, as by gathering information through observations, measurements in the field, questionnaires, or research of legal instruments, and data analysis in the support of planning, designing, and establishing of property boundaries. It involves the re-establishment of cadastral surveys and land boundaries based on documents of record and historical evidence, as well as certifying surveys (as required by statute or local ordinance) of subdivision plats or maps, registered land surveys, judicial surveys, and space delineation. Land surveying can include associated services such as mapping and related data accumulation, construction layout surveys, precision measurements of length, angle, elevation, area, and volume, as well as horizontal and vertical control surveys, and the analysis and utilization of land survey data.

History[edit]

Ancient surveying[edit]

A plumb rule from the book Cassells' Carpentry and Joinery

Basic surveyance has occurred since humans built the first large structures. The prehistoric monument at Stonehenge (c. 2500 BC) was set out by prehistoric surveyors using peg and rope geometry.[1]

In ancient Egypt, when the Nile River overflowed its banks and washed out farm boundaries, boundaries were re-established by a rope stretcher, or surveyor, through the application of simple geometry. The almost perfect squareness and north-south orientation of the Great Pyramid of Giza, built c. 2700 BC, affirm the Egyptians' command of surveying. The Groma surveying instrument originated in Mesopotamia (early 1st millennium BC).[2]

The mathmetician Liu Hui described ways of measuring distant objects in his work Haidao suanjing or The Sea Island Mathematical Manual, published in 263 AD.

The Romans recognized land surveyors as a profession. They established the basic measurements under which the Roman Empire was divided, such as a tax register of conquered lands (300 AD).[3]

In medieval Europe, the practice of beating the bounds was the practice of gathering a group of residents and walking around the boundaries of a parish or village to establish a communal memory of the boundaries. Young boys were included to ensure the memory lasted as long as possible.

In England, the Domesday Book was commissioned by William the Conqueror in 1086. It recorded the names of all the land owners, the area of land they owned, the quality of the land, and specific information of the area's content and inhabitants, although it did not include maps showing exact locations.

Modern surveying[edit]

Abel Foullon described a plane table in 1551, but it is thought that the instrument was in use earlier as his description is of a developed instrument.

Gunter's chain, introduced in 1620 by English mathematician Edmund Gunter, enabled plots of land to be accurately surveyed and plotted for legal and commercial purposes.

Table of Surveying, 1728 Cyclopaedia

In the 18th century, modern techniques and instruments for surveying began to be used. The modern theodolite, a precision instrument for measuring angles in the horizontal and vertical planes, was introduced by Jesse Ramsden in 1787. He created his great theodolite using an accurate dividing engine of his own design. Leonard Digges, Joshua Habermel and Jonathan Sisson[4] invented more primitive devices in the previous centuries, but Ramsden's theodolite represented a great step forward in the instrument's accuracy. William Gascoigne invented an instrument that used a telescope with an installed crosshair as a target device, in 1640. James Watt developed an optical meter for the measuring of distance in 1771; it measured the parallactic angle from which the distance to a point could be deduced.

The modern systematic use of triangulation was introduced by the Dutch mathematician Willebrord Snellius (a.k.a. Snell). In 1615 he surveyed the distance from Alkmaar to Bergen op Zoom, approximately 70 miles (110 kilometres), using a chain of quadrangles containing 33 triangles in all. Snell calculated how the planar formulae could be corrected to allow for the curvature of the earth. He also showed how to resection, or calculate, the position of a point inside a triangle using the angles cast between the vertices at the unknown point. These could be measured more accurately than bearings of the vertices, which depended on a compass. This established the key idea of surveying a large-scale primary network of control points first, and then locating secondary subsidiary points later, within that primary network. Between 1733 and 1740, Jacques Cassini and his son César undertook the first triangulation of France, including a re-surveying of the meridian arc, leading to the publication in 1745 of the first map of France constructed on rigorous principles.

A map by the Great Trigonometrical Survey, produced in 1870

Triangulation methods were by then well established for local map-making, but it was only towards the end of the 18th century that detailed triangulation network surveys were established to map whole countries. A team from the Ordnance Survey of Great Britain, originally under General William Roy, began the Principal Triangulation of Britain using the specially built Ramsden theodolite in 1783. This survey was finally completed in 1853. The Great Trigonometric Survey of India, which ultimately named and mapped Mount Everest and the other Himalayan peaks, was begun in 1801. The Indian survey had an enormous scientific impact; it was responsible for one of the first accurate measurements of a section of an arc of longitude, and for measurements of the geodesic anomaly. Surveying became a professional occupation in high demand at the turn of the 19th century with the onset of the Industrial Revolution. Surveyors were used on industrial infrastructure projects, such as canals, roads and rail, and the profession developed more accurate instruments to aid its work.

In the USA, the Land Ordinance of 1785 created the Public Land Survey System, which formed the basis for dividing the western territories into sections to allow the sale of land. States were divided into township grids which were further divided into sections and fractions of sections.

Napoleon Bonaparte founded continental Europe's first cadastre in 1808. This gathered data on the number of parcels of land, their value, land usage, and names. This system soon spread around Europe.

Robert Torrens introduced the Torrens system in South Australia in 1858. Torrens intended to simplify land transactions and provide reliable titles via a centralized register of land. The Torrens system was adopted in several other nations of the English-speaking world.

20th century[edit]

At the beginning of the century surveyors still faced the problem of accurate measurement of long distances, despite improvements over the older measuring chains and ropes. During the 1950s, Dr Trevor Lloyd Wadley developed the Tellurometer, which measures long distances using two microwave transmitter/receivers.[5] During the late 1950s Geodimeter introduced electronic distance measurement (EDM) equipment,[6] using the principles of measuring the phase shift of light waves[7] which are still used by modern instruments. These instruments saved the need for days or weeks of chain measurement by measuring between points kilometers apart in one go.

Advances in electronics allowed miniaturization of EDM. In the 1970s the first instruments combining angle and distance measurement were produced, becoming known as total stations. Manufacturers gradually added more equipment such as tilt compensators, data recorders, and onboard calculation programs, bringing improvements in accuracy and speed of measurement.

The first Satellite positioning system was the U.S. Navy TRANSIT system. The first successful launch took place in 1960. The system's primary purpose was to provide position information to Polaris missile submarines, but surveyors could use field receivers to determine the location of a point. The small number of satellites and bulky equipment made observations slow, difficult, and inaccurate; so usage of this system was limited to establishing benchmarks in remote locations.

The US Air force launched the first prototype satellites of the Global Positioning System (GPS) in 1978. GPS used a larger constellation of satellites and improved signal transmission to provide more accuracy. Early GPS observations required several hours of observations by a static receiver to reach survey accuracy requirements. Recent improvements to both the satellites and the receivers allow high-accuracy measurements by using a fixed base station and a second roving antenna, known as Real Time Kinematic (RTK) surveying.

21st century[edit]

The theodolite, total station, and RTK GPS survey remain the primary methods in use.

Remote sensing and satellite imagery continue to improve and become cheaper, allowing more commonplace use. New technologies which have become prominent include three-dimensional (3D) scanning and the use of lidar for topographical surveys.

Surveying equipment[edit]

A German engineer surveying during the First World War, 1918

The main surveying instruments in use around the world are the theodolite and steel band, the total station, the level and rod and surveying GPS systems. Most instruments are placed on a tripod when in use. Tape measures are often used for measurement of smaller distances. 3D scanners and various forms of aerial imagery are also used.

The Theodolite is an instrument for the measurement of angles. It uses two separate circles, protractors or alidades to measure angles in the horizontal and the vertical plane. A telescope mounted on trunnions can be aligned vertically with the target object, while the whole upper section rotates for horizontal alignment. The vertical circle measures the angle that the telescope makes against the vertical, known as the vertical angle. The horizontal circle uses an upper and lower plate. When beginning the survey, the instrument is pointed towards a known direction (bearing), and the lower plate is clamped into place. The instrument can then be rotated to measure the bearing to other objects. If no bearing is known or direct angle measurement is desired, the instrument can be set to zero during the initial sight and the readings will then be the angle formed between the initial object, the theodolite itself, and the item that the telescope is aligned with.

The Gyrotheodolite is a form of theodolite that uses a gyroscope to orient itself in the absence of reference marks. It is used in underground applications.

The total station is a development of the theodolite with an electronic distance measurement device (EDM). A total station can also be used for leveling when set to the horizontal plane. Since their introduction, total stations have shifted from optical-mechanical to fully electronic devices.[citation needed]

Modern top-of-the-line total stations no longer need a reflector or prism to return the light pulses used for distance measurements. They are fully robotic, and can even e-mail point data to a remote computer and connect to satellite positioning systems, such as Global Positioning System.Real Time Kinematic GPS systems have increased the speed and precision of surveying, but they are still only horizontally accurate to about 20 mm and vertically to 30–40 mm.[8]

GPS surveying differs from other GPS users in the equipment and methods used. Static GPS uses two receivers placed in position for a considerable length of time. The long span of time allows the receiver to compare a large amount of measurements as the satellites move through the sky, ensuring that the measurement network contains well conditioned geometry. This produces an accurate baseline that can be very long. (over 20 km) RTK surveying uses one static antenna to monitor changes in the satellite positions and atmospheric conditions, and a roving antenna that is used to move from one survey measurement to the next. The two antennas are linked by a radio signal that allows the static antenna to send corrections to the roving antenna. The roving antenna then applies those corrections to the GPS signals it is receiving to calculate its own position. RTK surveying is used over smaller distances than Static methods because the conditions further away from the base station will become too different to allow accurate measurement.

Surveying instruments have characteristics that make them suitable for certain uses. In first world countries, theodolites and levels are often used by constructors rather than surveyors because they are relatively cheap and let the constructor perform simple survey tasks by themselves. Total stations are versatile and are reliable in all conditions, making them a workhorse for many professional surveyors. The productivity improvements from a GPS, especially on larger scale surveys, makes them popular for major infrastructure or data gathering projects. One-person robotic-guided total stations allow surveyors to gather precise measurements without extra workers to look through and turn the telescope or record data. A fast but expensive way to measure large areas is with a helicopter, equipped with a laser scanner, combined with a GPS to determine the position and elevation of the helicopter. To increase precision, surveyors place beacons on the ground (about 20 km (12 mi) apart). This method reaches precisions between 5–40 cm (depending on flight height).[9]

Surveyors make use of ancillary equipment such as tripods and instrument stands, staves and beacons used for sighting purposes, PPE, vegetation clearing equipment, digging implements for finding survey markers that have been buried over time, hammers for placements of markers in various surfaces and structures, and portable radios for communication over long lines of sight.

Surveying techniques[edit]

A standard Brunton Geo compass, still used commonly today by geographers, geologists and surveyors for field-based measurements
Example of modern equipment for surveying (Field-Map technology): GPS, laser rangefinder and field computer allows surveying as well as cartography (creation of map in real-time) and field data collection.

Surveyors determine the position of objects by measuring angles and distances, along with various factors that can affect the accuracy of their observations. From this information, they can calculate constructs such as vectors, bearings, co-ordinates, elevations, areas, volumes, plans and maps. Measurements are also often split into horizontal and vertical components to simplify calculation. GPS and astronomic measurements also need measurement of a time component.

Distance measurement[edit]

Historically, distances were measured using a variety of means. These included chains having links of a known length such as a Gunter's chain, or measuring tapes made of steel or invar. To measure horizontal distances, these chains or tapes were pulled taut to reduce sagging and slack. The distance also had to be adjusted for heat expansion. Additionally, attempts to hold the measuring instrument level would be made. In instances of measuring up a slope, the surveyor might have to "break" (break chain) the measurement- use an increment less than the total length of the chain. Perambulators, or measuring wheels, were used to measure longer distances but not to a high level of accuracy. Tacheometry is the science of measuring distances by measuring the angle between two ends of an object with a known size. It was sometimes used prior to the invention of EDM where rough ground made chain measurement impractical.

Angle measurement[edit]

Historically, horizontal angles were measured by using a compass to provide a magnetic bearing, from which deflections could be measured. This type of instrument was later improved, with more precise scribed discs providing better angular resolution, and through mounting telescopes with reticles for more precise sighting atop the disc (see theodolite). Levels and calibrated circles allowing measurement of vertical angles were added, along with verniers for measurement to a fraction of a degree—such as with a turn-of-the-century transit.

The Plane table provided a graphical method of recording and measuring angles, which reduced the amount of mathematics required.

By observing the bearing from every vertex in a figure, a surveyor can measure around the figure and the final observation will be between the two points first observed, except with a 180° difference. This is called a close. If the first and last bearings are different, this shows the error in the survey, which is called the angular misclose. The surveyor can use this information to prove that the work meets the expected standards.

Levelling[edit]

Main article: Levelling

The simplest method for measuring height is with an altimeter – basically a barometer – using air pressure as an indication of height. But when more precise measurements are needed, a variety of means, such as precise levels (also known as differential leveling), have been developed to do this. When precise leveling, a series of measurements between two points are taken using an instrument and a measuring rod. Differentials in height between the measurements are added and subtracted in a series to obtain the net difference in elevation between the two endpoints of the series. With the advent of the Global Positioning System (GPS), elevation can also be measured with sophisticated satellite receivers, but usually with somewhat less accuracy than with traditional precise leveling. However, the accuracy may be similar to a long-distance traditional leveling run.

When using an optical level, the endpoint may be out of the effective range of the instrument, or there may be obstructions or large changes of elevation between the endpoints. In these situations, multiple setups are needed. Turning is a term used when referring to moving the level to take an elevation shot from a different location. To "turn" the level, one must first take a reading and record the elevation of the point the rod is located on. While the rod is being kept in exactly the same location, the level is moved to a new location where the rod is still visible. A reading is taken from the new location of the level and the height difference is used to find the new elevation of the level gun. This is repeated until the series of measurements is completed. Because the level must be horizontal to obtain a valid measurement, if the horizontal crosshair of the instrument is lower than the base of the rod, the surveyor will not be able to sight the rod and get a reading. The rod can usually be raised up to 25 feet high, allowing the level to be set much higher than the base of the rod.

Determining position[edit]

The primary way of determining one's position on the earth's surface when no known positions are nearby is by astronomic observations. Observations to the sun, moon and stars could all be made using navigational techniques. Once the instrument's position and bearing to a star is determined, the bearing can be transferred to a reference point on the earth and which can then be used as a base for further observations. Survey-accurate astronomic positions were difficult to observe and calculate and so tended to be a base off which many other measurements were made. Since the advent of the GPS system, astronomic observations are rare as GPS allows adequate positions to be determined over most of the surface of the earth.

Reference networks[edit]

Main article: Geodetic network
A survey using traverse and offset measurements to record the location of the shoreline shown in blue. Black dashed lines are traverse measurements between reference points (black circles). The red lines are offsets measured at right angles to the traverse lines.

Few survey positions are derived from first principles. Instead, most surveys points are measured relative to previously measured points. This forms a reference or control network where each point can be used by a surveyor to determine their own position when beginning a new survey.

Survey points are usually marked on the earth's surface by objects ranging from small nails driven into the ground to large beacons that can be seen from long distances. The surveyors can set up their instruments on this position and measure to nearby objects. Sometimes a tall, distinctive feature such as a steeple or radio aerial has its position calculated as a reference point that angles can be measured against.

Triangulation is a method of horizontal location favoured in the days prior to EDM and GPS measurement. With the triangulation method, distances, elevations and directions between objects at great distance from one another can be determined. Since the early days of surveying, this was the primary method of determining accurate positions of objects for topographic maps of large areas. A surveyor first needs to know the horizontal distance between two of the objects, known as the baseline. Then the heights, distances and angular position of other objects can be derived, as long as they are visible from one of the original objects. High-accuracy transits or theodolites were used for this work, and angle measurements between objects were repeated for increased accuracy. See also Triangulation in three dimensions.

Offsetting is an alternate method of determining position of objects, and was often used to measure imprecise features such as riverbanks. The surveyor would mark and measure two known positions on the ground roughly parallel to the feature, and mark out a baseline between them. At regular intervals, a distance was measured at right angles from the first line to the feature. The measurements could then be plotted on a plan or map, and the points at the ends of the offset lines could be joined to show the feature.

Traversing is a common method of surveying smaller areas. Starting from an old reference mark or known position, the surveyor creates a network of reference marks covering the area to be surveyed and then measures bearings and distances between the reference marks, and to the features to be surveyed. Most traverses form a loop pattern or link between two prior reference marks to allow the surveyor to check their measurements are correct.

Datum and coordinate systems[edit]

Many surveys do not calculate positions on the surface of the earth, but instead measure the relative positions of objects. However, often the surveyed items need to be compared to outside data, such as boundary lines or previously surveyed objects. The oldest way of describing a position is via latitude and longitude, and often a height above sea level. However, as the surveying profession grew, attempts were made to create Cartesian coordinate systems that simplified the mathematics for surveys which took place over small portions of the earth. The simplest coordinate systems assume that the earth is flat and measure from an arbitrary point, known as a 'datum' (singular form of data). The coordinate system allows easy calculation of the distances and direction between objects, but only over a small area due to the earth's curvature. North is often defined as true north at the datum.

For larger regions, it is necessary to model the shape of the earth using an ellipsoid or a geoid. Many countries have created coordinate-grids that are customized to minimize error in their area of the earth.

Errors and accuracy[edit]

A basic tenet of surveying is that no measurement is perfect, and that there will always be a small amount of error.[10] Survey errors are classed into three types:

  • Gross errors or blunders: are errors made by the surveyor during the survey, for example, upsetting the instrument, misaiming a target, or writing down a wrong measurement. A large gross error may reduce the accuracy to an unacceptable level. Therefore surveyors use redundant measurements and independent checks to detect these errors early in the survey.
  • Systematic errors: are errors that follow a consistent pattern. Examples include effects of temperature on a chain or EDM measurement, or a poorly adjusted spirit-level resulting in a misaligned instrument or target pole. Systematic errors that have known effects can be compensated or corrected.
  • Random errors: Random errors are the small unavoidable measurements caused by imperfections in measuring equipment, eyesight, and conditions. They can be minimized by redundancy of measurement and avoiding unstable conditions. Random errors tend to cancel each other out, but checks must be made to ensure they are not propagating from one measurement to the next.

Surveyors avoid propagating errors by ensuring that their equipment is in good condition, using consistent measurement and recording methods, and by good design of their survey reference network. Redundancy of measurements allows the use of averaging and allows outlier measurements to be discarded. Independent checks such as measuring a point from two or more locations or using two different methods means that errors can be detected by comparing the results of the two measurements.

Once the surveyor has calculated the magnitude of the errors in his work, it is adjusted. This is the process of distributing the error between all measurements. Each observation is weighted according to how much of the total error it is likely to have caused and part of that error is allocated to it in a proportional way. The most common methods of adjustment are the Bowditch method and the Principle of least squares method.

The Surveyor must be able to distinguish between accuracy and precision. In the United States, surveyors and civil engineers use units of feet wherein a survey foot is broken down into 10ths and 100ths. Many deed descriptions requiring distance calls are often expressed using these units (125.25 ft). On the subject of accuracy, surveyors are often held to a standard of one one-hundredth of a foot; about 1/8 inch. Calculation and mapping tolerances are much smaller wherein achieving near-perfect closures are desired. Though tolerances such as this will vary from project to project, in the field and day to day usage beyond a 100th of a foot is often impractical.

Types of surveys[edit]

Specializations of surveying may be classed differently according to the local professional organisation or regulatory body, but broad groups are:

  • As-built survey: a survey carried out during or immediately after a construction project for record, completion evaluation and payment purposes. An as-built survey is also known as a 'works as executed survey' and documents the location of the recently constructed elements that are subject to completion evaluation. As built surveys are often presented in red or redline and overlaid over existing design plans for direct comparison with design information.
  • Cadastral or boundary surveying: a survey that establishes or re-establishes boundaries of a parcel using its legal description, which involves the setting or restoration of monuments or markers at the corners or along the lines of the parcel, often in the form of iron rods, pipes, or concrete monuments in the ground, or nails set in concrete or asphalt. A mortgage survey or physical survey is a simple survey that delineates land boundaries and building locations. In many places a mortgage survey is required by lending institutions as a precondition for a mortgage loan. The ALTA/ACSM Land Title Survey is a surveying standard proposed by the American Land Title Association and the American Congress on Surveying and Mapping that incorporates elements of the boundary survey, mortgage survey, and topographic survey.
  • Control surveying: Control surveys establish reference points that surveyors can use to establish their own position at the start of future surveys. Most other forms of surveying will contain elements of control surveying.
  • Construction surveying
  • Deformation survey: a survey to determine if a structure or object is changing shape or moving. The three-dimensional positions of specific points on an object are determined, a period of time is allowed to pass, these positions are then re-measured and calculated, and a comparison between the two sets of positions is made.
  • Dimensional control survey: This is a type of survey conducted in or on an non-level surface. Common in the oil and gas industry to replace old or damaged pipes on a like-for-like basis, the advantage of dimensional control survey is that the instrument used to conduct the survey does not need to be level. This is useful in the off-shore industry, as not all platforms are fixed and are thus subject to movement.
  • Engineering surveying: those surveys associated with the engineering design (topographic, layout, and as-built) often requiring geodetic computations beyond normal civil engineering practice.
  • Foundation survey: a survey done to collect the positional data on a foundation that has been poured and is cured. This is done to ensure that the foundation was constructed in the location, and at the elevation, authorized in the plot plan, site plan, or subdivision plan.
  • Hydrographic survey: a survey conducted with the purpose of mapping the shoreline and bed of a body of water for navigation, engineering, or resource management purposes.
  • Leveling: either finds the elevation of a given point or establish a point at a given elevation.
  • Measured survey : a building survey to produce plans of the building. such a survey may be conducted before renovation works, for commercial purpose, or at end of the construction process.
  • Mining surveying: Mining surveying includes directing the digging of mine shafts and galleries and the calculation of volume of rock. It uses specialised techniques due to the restraints to survey geometry such as vertical shafts and narrow passages.
  • Mortgage survey produces a plan needed by lending institutions to verify all principle structures are on the locus property, that none of the neighbors encroach, required setbacks are met and bordering flood zones are indicated.
  • Photographic control survey: A survey that creates reference marks visible from the air to allow aerial photographs to be rectified.
  • Stakeout, Layout or Setout: an element of many other surveys where the calculated or proposed position of an object is marked on the ground. This can be temporary or permanent. This is an important component of engineering and cadastral surveying.
  • Structural survey: a detailed inspection to report upon the physical condition and structural stability of a building or other structure and to highlight any work needed to maintain it in good repair.
  • Topographic survey: a survey that measures the elevation of points on a particular piece of land, and presents them as contour lines on a plot.

The surveying profession[edit]

See also: Geomatics
The pundit (explorer) cartographer Nain Singh Rawat (19th century) received a Royal Geographical Society gold medal in 1876, for his efforts in exploring the Himalayas for the British
An all-female surveying crew in Idaho, 1918

The basic principles of surveying have changed little over the ages, but the tools used by surveyors have evolved. Engineering, especially civil engineering, often needs surveyors.

Wherever roads, railways, reservoirs, dams, pipeline transports, retaining walls, bridges, or residential areas are built, surveyors help determine the placement of structures. They establish the boundaries of legal descriptions and political divisions. They also provide advice and data for geographical information systems (GIS) that contain data on land features and boundaries.

Surveyors must have a thorough knowledge of algebra, basic calculus, geometry, and trigonometry. They must also know the laws that deal with surveys, real property, and contracts.

Most jurisdictions recognize three different levels of qualification:

Survey assistants or chainmen are usually unskilled workers who help the surveyor. They place target reflectors, find old reference marks, and mark points on the ground. The term 'chainman' derives from past use of measuring chains, when an assistant was needed to move the end of the chain under the surveyor's direction.

Survey technicians may be qualified or unqualified and their roles may include operation of survey instruments, running of surveys in the field, survey calculations, and drafting of plans. A technician usually has no legal authority and cannot certify his work. Qualifications at the certificate or diploma level are most common.

Licensed, registered, or chartered surveyors usually hold a degree or higher qualification and are often required to pass further exams to gain entrance to a professional association or to gain their certification status. Surveyors are responsible for planning and management of surveys and ensuring that their surveys, or surveys performed under their supervision, meet the necessary legal standards. Many principals of surveying firms hold this status.

Informal surveying[edit]

Not all surveys are carried out by professional surveyors. Depending on the jurisdiction and circumstances, the builders of a structure may set it out themselves. A surveyor often lays out the most significant corners and the builders then lay out the rest of the building themselves using a variety of techniques.

Licensing[edit]

Licensing requirements vary with jurisdiction, and are commonly consistent within national borders.

USA[edit]

In most of the United States, surveying is recognized as a distinct profession apart from engineering.

Licensing requirements vary by state, but they have components of education, experience, and examinations. In the past, experience gained through an apprenticeship, together with passing a series of state-administered examinations, was required to attain licensure. Now, most states insist upon the basic qualification of a degree in surveying, plus experience and examination requirements.

The licensing process follows two phases. First, upon graduation, the candidate may be eligible to take the Fundamentals of Surveying (FS) exam, to be certified upon passing and meeting all other requirements as a surveying intern (SI),(formerly surveyor in training (SIT)). Upon being certified as an SI, the candidate then needs to gain additional on-the-job experience to become eligible for the second phase. That typically consists of the Principles and Practice of Land Surveying (PS) exam, along with a state-specific examination.

Licensed surveyors usually denote themselves with the letters P.L.S. (professional land surveyor), P.S. (professional surveyor), L.S. (land surveyor), R.L.S. (registered land surveyor), R.P.L.S. (Registered Professional Land Surveyor), or P.S.M. (professional surveyor and mapper) following their names, depending upon the dictates of their particular jurisdiction of registration.

Canada[edit]

In Canada, land surveyors are registered to work in their respective province. The designation for a land surveyor breaks down by province, but follows the rule whereby the first letter indicates the province, followed by L.S. There is also a designation as a C.L.S. or Canada lands surveyor, who has the authority to work on Canada lands, which include Indian Reserves, National Parks, the three territories, and offshore lands.

Commonwealth[edit]

In many Commonwealth countries, the term Chartered Land Surveyor is used for someone holding a professional license to conduct surveys.

Legal aspects[edit]

A licensed land surveyor is generally required to sign and seal all plans, the format of which is dictated by their state jurisdiction, showing their name and registration number.

In many jurisdictions, when setting boundary corners land surveyors are also required to place survey monuments bearing their registration numbers in the form of capped iron rods, concrete monuments, or nails with washers.

Surveying students with their professor at the Helsinki University of Technology in the late 19th century

Surveying institutions[edit]

Most countries' governments regulate at least some forms of surveying, via a survey agency which establishes regulations and standards. Standards often deal with accuracy tolerances, who is allowed to call themselves a surveyor, types of monumentation used for boundaries, and maintenance of geodetic networks. Many nations devolve this authority to regional entities or states/provinces. Cadastral surveys tend to be the most regulated because of the permanence of the work: lot boundaries established by a cadastral survey may stand for hundreds of years without modification.

Most jurisdictions also have a form of professional institution representing the surveyors as a whole. These institutes often have a hand in endorsing or licensing potential surveyors, as well as in setting and enforcing ethical standards. The largest such institution is International Federation of Surveyors (Abbreviated FIG, for French: Fédération Internationale des Géomètres), which represents the survey industry worldwide.

Building surveying[edit]

In the United States, Canada, the United Kingdom and most Commonwealth countries building surveying is considered to be a distinct profession. Land surveyors have their own professional associations and licencing requirements. The services of a licenced land surveyor are required for boundary surveys (to establish the boundaries of a parcel using its legal description) and subdivision plans (a plot or map based on a survey of a parcel of land, with boundary lines drawn inside the larger parcel to indicated the creation of new boundary lines and roads).

Cadastral surveying[edit]

Main article: Cadastral surveying

One of the primary roles of the land surveyor is to determine the boundary of real property on the ground. That boundary has already been established and described in legal documents and official plans and maps prepared by attorneys, engineers, and other land surveyors. The corners of the property will either have been monumented by a prior surveyor, or by the surveyor hired to perform the survey of the new boundary which has been agreed upon by adjoining land owners.

Cadastral land surveyors are licensed by governments. Most cadastral surveys in the United States are conducted by the federal government through the Cadastral Surveys branch of the Bureau of Land Management (BLM), formerly the General Land Office (GLO).[11] They consult with U.S. Forest Service, National Park Service, U.S. Army Corps of Engineers, Bureau of Indian Affairs, U.S. Fish and Wildlife Service, U.S. Bureau of Reclamation, et.al.

In states organized per the Public Land Survey System (PLSS), surveyors must carry out BLM cadastral surveys under that system.

Cadastral surveyors often have to work around changes to the earth that obliterate or damage boundary monuments. When this happens, they must consider evidence that is not recorded on the title deed. This is known as extrinsic evidence.[12]

F.V. Hayden's map of Yellowstone National Park, 1871. His surveys were a significant basis for establishing the park in 1872.

The art of land surveying[edit]

Many properties have considerable problems with regard to improper bounding or miscalculations in past surveys, titles, easements, and wildlife crossings. Many properties are created from multiple divisions of a larger piece over the course of years, and with every additional division the risk of miscalculation increases. Abutting properties might not coincide with adjacent parcels, resulting in hiatuses (gaps) and overlaps. Many times a surveyor must solve a puzzle using pieces that do not exactly fit together. In these cases, the solution uses the surveyor's research and interpretation, along with established procedures for resolving discrepancies. This is in essence a process of continual error correction and update; where official records countermand the previous and sometimes erroneous survey documents recorded by older monuments and older survey methods.[13]

See also[edit]

References[edit]

  1. ^ Johnson, Anthony, Solving Stonehenge: The New Key to an Ancient Enigma. (Thames & Hudson, 2008) ISBN 978-0-500-05155-9
  2. ^ Hong-Sen Yan & Marco Ceccarelli (2009), International Symposium on History of Machines and Mechanisms: Proceedings of HMM 2008, Springer, p. 107, ISBN 1-4020-9484-1 
  3. ^ Lewis, M. J. T. (2001-04-23). Surveying Instruments of Greece and Rome. Cambridge University Press. ISBN 9780521792974. Retrieved 30 August 2012. 
  4. ^ Turner, Gerard L'E. Nineteenth Century Scientific Instruments, Sotheby Publications, 1983, ISBN 0-85667-170-3
  5. ^ Sturman, Brian; Wright, Alan. "The History of the Tellurometer" (PDF). http://www.fig.net/. International Federation of Surveyors. Retrieved 20 July 2014. 
  6. ^ Cheves, Marc. "Geodimeter-The First Name in EDM". http://www.profsurv.com/magazine/. Retrieved 2014-07-20. 
  7. ^ Mahun, Jerry. "Electronic Distance Measurement". Jerrymahun.com. Retrieved 2014-07-20. 
  8. ^ National Cooperative Highway Research Program: Collecting, Processing and Integrating GPS data into GIS, p. 40. Published by Transportation Research Board, 2002 ISBN 0-309-06916-5, ISBN 978-0-309-06916-8
  9. ^ Toni Schenk, Suyoung Seo, Beata Csatho: Accuracy Study of Airborne Laser Scanning Data with Photogrammetry, p. 118
  10. ^ Kahmen, Heribert; Faig, Wolfgang (1988). Surveying. Berlin: de Gruyter. p. 9. ISBN 3-11-008303-5. Retrieved 2014-08-10. 
  11. ^ A History of the Rectangular Survey System by C. Albert White, 1983, Pub: Washington, D.C. : U.S. Dept. of the Interior, Bureau of Land Management : For sale by Supt. of Docs., U.S. G.P.O.,
  12. ^ Richards, D., & Hermansen, K. (1995). Use of extrinsic evidence to aid interpretation of deeds. Journal of Surveying Engineering, (121), 178.
  13. ^ http://www.state-engineering.com/land_surveying.html

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